Add automatic offline update pre condition

Signed-off-by: Sudarshan C <P&lt;sudarshan.cp2@in.bosch.com>

content/guides/ostree.md

@@ -69,6 +69,23 @@ with special name `static-update.bundle` and attach that device into
 the target system. AUM will automatically detect the update file and try
 to use it for the system upgrade.
 
+{{% notice info %}}
+Automatic offline updates will only be triggered when a file with the above
+mentioned special name is found on a USB drive with a single partition.
+To create a USB disk with a single partition in Apertis:
+- Insert USB device and ensure that it is visible to the Apertis SDK.
+- Use `lsblk` or another tool to determine the disk device file related to the USB device.
+- Create a new partition spanning the USB device (**warning**: this will delete existing data):
+  ```
+  $ echo 'type=83' | sudo sfdisk $DISK
+  ```
+  Where `DISK` is set to the name and location of the disk device file (for example: `/dev/sda`)
+- Format this new partition wit a FAT32 file system:
+  ```
+  $ sudo mkfs -t vfat $DISK
+  ```
+{{% /notice %}}
+
 ### Manual offline update
 
 It is possible to update the system manually from local file with CLI,